Microeconomics Study Guide: Demand, Supply, and Market Equilibrium

Demand, Supply, and Market Equilibrium

Introduction

This study guide covers foundational microeconomic concepts including demand, supply, market equilibrium, and the effects of various changes on equilibrium price and quantity. These topics are essential for understanding how markets function and respond to external events.

Demand and Supply: Key Concepts

• Demand: The quantity of a good or service that consumers are willing and able to purchase at various prices during a given period.

• Supply: The quantity of a good or service that producers are willing and able to offer for sale at various prices during a given period.

• Equilibrium Price (P): The price at which the quantity demanded equals the quantity supplied.

• Equilibrium Quantity (Q): The quantity bought and sold at the equilibrium price.

Determinants of Demand and Supply

• Determinants of Demand:

  • Consumer income

  • Prices of related goods (substitutes and complements)

  • Tastes and preferences

  • Expectations about future prices

  • Population size

• Determinants of Supply:

  • Input prices

  • Technology

  • Number of sellers

  • Expectations about future prices

  • Government policies (taxes, subsidies, regulations)

Shifts vs. Movements Along Curves

• Movement along the curve: Caused by a change in the price of the good itself.

• Shift of the curve: Caused by changes in non-price determinants (e.g., income, tastes, input costs).

Market Equilibrium

Market equilibrium occurs where the demand and supply curves intersect. At this point, the market clears, and there is no tendency for price to change unless an external factor shifts demand or supply.

• Equilibrium Condition:

  • $Q_d = Q_s$

• Adjustment to Equilibrium:

  • If $Q_d > Q_s$, there is a shortage; price tends to rise.

  • If $Q_s > Q_d$, there is a surplus; price tends to fall.

Effects of Changes in Demand and Supply

• Increase in Demand: Raises equilibrium price and quantity.

• Decrease in Demand: Lowers equilibrium price and quantity.

• Increase in Supply: Lowers equilibrium price, raises equilibrium quantity.

• Decrease in Supply: Raises equilibrium price, lowers equilibrium quantity.

• Simultaneous Changes: The effect on price and quantity depends on the relative magnitude of shifts in demand and supply.

Examples and Applications

• Natural Disasters: A hurricane destroying crops (e.g., oranges) decreases supply, shifting the supply curve left, raising price and lowering quantity.

• Health Announcements: If research finds a food reduces disease risk, demand increases, shifting the demand curve right, raising both price and quantity.

• Technological Advancements: Increase supply by lowering production costs, shifting supply curve right, lowering price and increasing quantity.

• Income Changes: For normal goods, higher income increases demand; for inferior goods, higher income decreases demand.

Shortages and Surpluses

• Shortage: Occurs when quantity demanded exceeds quantity supplied at the current price. Evidence includes rising prices and consumers competing for limited goods.

• Surplus: Occurs when quantity supplied exceeds quantity demanded at the current price. Evidence includes falling prices and unsold goods.

Law of Supply and Law of Demand

• Law of Demand: As price increases, quantity demanded decreases, ceteris paribus.

• Law of Supply: As price increases, quantity supplied increases, ceteris paribus.

Market Forces and Equilibrium Adjustment

• When not at equilibrium, market forces push price toward equilibrium.

• Surplus: Price falls until equilibrium is reached.

• Shortage: Price rises until equilibrium is reached.

Table: Effects of Shifts in Demand and Supply on Equilibrium

Change	Equilibrium Price	Equilibrium Quantity
Increase in Demand	Increases	Increases
Decrease in Demand	Decreases	Decreases
Increase in Supply	Decreases	Increases
Decrease in Supply	Increases	Decreases
Increase in Demand & Supply	Depends on relative magnitude	Increases
Decrease in Demand & Supply	Depends on relative magnitude	Decreases

Formulas and Equations

• Equilibrium Condition:

  • $Q_d = Q_s$

• Law of Demand:

  • $Q_d = f(P)$, where $Q_d$ decreases as $P$ increases

• Law of Supply:

  • $Q_s = f(P)$, where $Q_s$ increases as $P$ increases

Additional info:

• Questions in the file cover scenarios such as changes in consumer income, technological advancements, natural disasters, and government policies, all of which affect demand and supply.

• Examples include markets for oranges, walnuts, Blu-ray players, gasoline, and gold, illustrating the application of these concepts.